ZIMSEC O-Level Biology (4025)

Reproduction and Growth: notes

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Asexual reproduction: one parent, offspring identical. Examples: runners, bulbs, binary fission.
Sexual reproduction: two gametes fuse, so offspring vary.
Flower: the anther makes pollen; the stigma receives it; the ovary holds ovules.
Pollination: transfer of pollen to a stigma, by insects or wind. Fertilisation: a male nucleus fuses with the ovule.
Germination needs: water, oxygen and a suitable temperature.
Human reproduction: testes make sperm; ovaries release an egg about every 28 days; the fertilised egg implants in the uterus.
Pregnancy: the placenta passes food and oxygen to the foetus and removes waste.
HIV: spread through unprotected sex, infected blood and from mother to child. It weakens the immune system.